1. Field of the Invention
The present invention relates to the manufacture of semiconductor devices, and more particularly, the present invention relates to the application of a resist material onto a wafer during the manufacture of semiconductor devices.
2. Related Art
In a photolithography process carried out during the manufacture of a semiconductor integrated circuit, it is necessary to apply a resist to a semiconductor wafer. Conventionally, as shown in FIG. 3, a wafer 1 is centered and held by a chuck 3, a resist 5 is dropped on the wafer 1, and the chuck 3 is rotated about its vertical axis. The rotation of the wafer 1 causes the resist 5 to spread over an entire surface of the wafer 1. The film thickness of the resist 5 is adjusted to a desired level by setting the rotating velocity and rotating time of the chuck 3.
In the apparatus shown in FIG. 3, however, when the resist has a high viscosity or the resist is applied on a substrate with poor wettability, certain defects such as those shown in FIG. 4 can result. In particular, the resist liquid can spatter upward resulting in poor application, or a bubble can become trapped at the interface between the resist and the wafer. In an effort to avoid such defects, it is sometimes necessary to apply excess resist onto the wafer.
An object of the present invention is to provide a method for manufacturing a semiconductor device, in which the application of resist can be achieved with a relatively small quantity resist material, even in the case where the resist has a high viscosity or the substrate has poor wettability.
In the first aspect of the present invention, there is provided a method for manufacturing a semiconductor device which includes placing a wafer onto a rotatable and liftable stage of a resist coating apparatus, the resist coating apparatus including a spin motor for rotating the stage and a lifting device for elevating the stage; setting an acceleration of the lifting device according to at least one of a viscosity of a resist material and a wettability of the wafer; dispensing the resist material onto an upper surface of the wafer; rotating the stage and the wafer to distribute the resist material over the upper surface of the wafer; and controlling the lifting device to elevate the stage and the wafer at the set acceleration while rotating the stage and the wafer.
In the second aspect of the present invention, there is provided a method for manufacturing a semiconductor device which includes placing a wafer onto a rotatable and liftable stage of a resist coating apparatus, the resist coating apparatus including a spin motor which rotates the stage and aerodynamic blades which are fixed to the stage and cause the stage to elevate when rotated; setting a maximum height to which the stage is elevated according to at least one of the viscosity of a resist material and the wettability of the wafer; dispensing the resist material onto an upper surface of the wafer; and rotating the stage and the wafer to distribute the resist material over the upper surface of the wafer, and to cause the aerodynamic blades to elevate the stage and the wafer while the resist material is being distributed over the upper surface of the wafer.